The method: update() updates the instance,
if it needs to reflect the change of the properties.

How to draw the instance

There are following cases to draw the instances.

Drawing compulsory

You make the flag of forced drawing "True"
to draw compulsory, and call the method:draw(),
because the method: draw() do not draw if it does not need.

object.redraw();

Drawing (ordinary)

Usually , we use the method: draw() to draw the instance.
it has a good performance, because it do not draw if do not need.

object.setAbsoluteDraw(Mwt.True);
object.draw();

Clearing the instance (no exposed event)

You can clear the instance with the method: clear(),
and draw it with draw().
The method: clear() does not creates the exposed event,
so, if the other instance which are overlapped exists,
its area is invalidated. In such case, use redraw() method
which creates the exposed event.

object.draw();

Clearing the instance (creates the exposed event)

You can redraw the instance with the method: redraw().
it creates the exposed event so that
the other overlapped instances are updated.
it can make the performance worse if there are many instances.